Reversible galvanic battery.



I UNITED i STATES PATENT THOMAS A. EDISON, oE LLEwELLYN PARK, NEWJERSEY.

REVERSIBLE GALVANIC BATTERY.

SPECIFICATION forming part of Letters PatentlNo. 721,682, dated March 3,1903.

Application filed November 28, 1902. Serial No. 133,119. (No model.) 7

T ttZZ whom, it ntcty' concern.-

Be it known that I, THOMAS A. EDISON, a citizen of the United States,residing at Llewellyn Park, Orange, in the county' of Essex and StateofNew Jersey, have invented a certain new and useful Improvement inReversible Galvanic Batteries, of which the following is a description;

My invention relates to reversible galvanic batteries of the typeemploying an alkaline electrolyte and insoluble electrolytically-activematerials; and the invention relates'particularly tothe oxidizableelement-namely, the element employing an active material which isoxidized on discharge and reduced during the charging operation.

. The invention consists in the'use of cobalt oxid, preferably mixedwith metallic mercury or with metallic mercury and copper or silver,whereby a great proportion of the cobalt oxid is kept in electricalcontact with the electrode and made electrolytically active in analkaline solution to form the oxidizable element on discharge.

The invention also consists inthe combination of such an element with asuitable depolarizerrfurnishing oxygen on discharge in an alkalineelectrolyte to form a complete reversible galvanic battery.

In order to produce the new element, I prefer to proceed substantiallyas follows: Dried oxalate of cobalt is first producedin any suit ableway and is ignited and kept at a low "temperature in the air until ithas been wholly decomposed to form. the anhydrous oxid of cobalt. Thisoxidis then mixed with preferably about fifteen per cent. ofprecipitated oxid of mercury ifan electrode is to loe obtained composedof cobalt and mercury, or, if desired, it may be mixed, preferably, withabout twenty-five per cent. of finely-divided metallic copper and sixper cent. of precipitated oxid of mercury if the resulting electrode isto be formed of cobalt and a combination of copper and mercury. Theseproportions of course may be varied; but those indicated give goodresults. I find, in fact,

that by increasing the proportion of mercury or of mercury and copper alarger proportion of the cobalt is rendered active; but the increase inefiiciency is secured, at a sacrifice of lightness and economy. Silvermay also be employed in place of the copper; but it possesses theobjection of being too expensive at the present time for economical use.

.The mixture ofoxid-of cobalt and oxid of mercury orof oxid of cobalt,metallic copper, and oxid of mercury is then mixed thoroughly, formedinto briquets, and utilized in any desired manner, preferably by beingsupported in perforated nickel-plated pockets or receptacles, which inturn are crimped in position within plates or grids, as I have describedin patents already granted to me.

,An electrode containing a mixture of cobalt and mercury or. of cobalt,mercury, and copper or silver is preferably employed in an alkalinesolution of, say, twenty per cent. of potassic-hydroxid in water opposedto a depolarizing element containing nickel hydroxid as the activematerial mixed with foliated or flake graphite. When such a combinationhas been charged and recharged several times, its average voltage isabout 1.10 volts. When such acombination isin afullycharged condition,the nickel hydroxid is raised to avery high state of oxidation and thecobalt is reduced, so far as its active particles are concerned, to themetallic state. On discharging the nickel hydroxid reverts to a lowercondition of oxidation, while the metallic cobalt is oxidized. Owing tothe relative ease, as compared to cobalt, with which mercury and copperreduf'ce, the added mercury or copper, or silver, if used, will bereduced to the metallic state when the battery is first charged, so asto procure good electrical contact between the ,active cobalt particles.Since the cobalt on discharge oxidizes muchmore readily'than eithermercury, copper, or silver, the;latter materials remain inmetallic-form, and their presence serves wholly to assist electricalconduction betweenthe particles of the active material. Although Iprefer to add a readily-reducible metal, like mercury, copper, orsilver, or

, such as flake graphite, can be used for maintaining the cobaltparticles in electrical contact. I

ICO

Having now described my invention, what I claim is- 1. An oxidizableelement for a reversible galvanic battery employing cobalt, which isoxidized on discharge, substantially as set forth.

2. In a reversible galvanic battery employing an alkaline electrolyte,an oxidizable element therefor employing cobalt, which is oxidized ondischarge, substantially as set forth.

3. An oxidizable element for a reversible galvanic battery employingcobalt as the active material, and a more readily reducible metal orcombination of such metals added thereto for preserving electricalcontact be tween the active particles, substantially as set forth.

4. In a reversible galvanic battery, an oxidizable element employingcobalt as the active material, mixed with metallic mercury forpreserving electrical contact between the active particles,substantially as set forth.

5. A reversible galvanic'battery employing cobalt as the activematerial, mixed with metallic mercury and another readily-reduciblemetal for preserving electrical contact between the active particles,substantially as set forth.

6. In a reversible galvanic battery, an oxidizable element thereforemploying cobalt as the active material, mixed with metallic mercury andmetallic copper for preserving electrical contact between the particlesof active material, substantially as set forth.

7. ha re versible galvanic battery, the combination with adepolarizing-electrode, of an oxidizable electrode employing cobalt asthe oxidizable material on discharge, substantially as set forth.

8. In a reversible galvanic battery employing an alkaline electrolyte,the combination with a depolarizing-electrode, of an oxidizableelectrode employing cobalt as the oxidizable active material 011discharge, substantially as set forth.

9. In a reversible galvanic battery, the combination with adepolarizing-electrode, of an oxidizable electrode employing cobalt asthe oxidizable material on discharge, and a readily-reducible metalmixed with the cobalt for preserving electrical contact between theactive particles, substantially as set forth.

10. In a reversible galvanic battery, the combination with adepolarizing-electrode, of an oxidizable electrode employing cobalt asthe oxidizable material on discharge, and metallic mercury mixed withthe cobalt for preserving electrical contact between the activeparticles, substantially as set forth.

11. In a reversible galvanic battery, the combination with adepolarizing-electrode, of an oxidizable electrode employing cobalt asthe oxidizable material on discharge, and metallic mercury and coppermixed with the cobalt for preserving electrical contact between theactive particles, substantially as set forth.

12. In a reversible galvanic battery, the combination with adepolarizing-electrode employing nickel hydroxid as the active material,of an oxidizable electrode employing cobalt as the oxidizable materialon discharge, substantially as set forth.

13. In a reversible galvanic battery, the combination with adepolarizing-electrode employing nickel hydroxid as the activemateterial, of an oxidizable electrode employing cobalt as theoxidizable material on discharge, and a readily-reducible metal mixedwith the cobalt for preserving electrical contact between the activeparticles, substantially as set forth.

14. In a reversible galvanic battery, the combination with adepolarizing-electrode employing nickel hydroxid as the'active material,of an oxidizable electrode employing cobalt as the oxidizable materialon discharge, and metallic mercury mixed with the cobalt for preservingelectrical contact between the active particles, substantially as setforth.

15. In a reversible galvanic battery, the combinationwithadepolarizing-electrode employing nickel hydroxid as the activematerial, of an oxidizable elect-rode employing cobalt as the oxidizablematerial on discharge, and metallic mercury and copper mixed with thecobalt for preserving electrical contact between the active particles,substantially as set forth.

This specification signed and witnessed this 13th day of November, 1902.

TIIOS. A. E DISON.

\Vitnesses:

FRANK L. DYER, J. E. RANDOLPH.

